The project is designed to develop new instrumentation and methodology or improve existing instrumentation and methodology for characterization of biological macromolecules and for studying their interactions. Analytical ultracentrifugation, the techniques ancillary to it, and methods of data analysis using mathematical modeling appropriate for these techniques are the major areas of interest. Improved precision and optimal efficiency in ultracentrifugal analysis requires improved methods of data acquisition. A microprocessor controlled system for the direct acquisition of data from the photomultiplier tube of the ultraviolet absorption scanner of the ultracentrifuge and for the control of that acquisition has been developed. The software requisite for making this system operational is presently in a developmental stage. When complete, this system will permit direct acquisition of data in digital form while the ultracentrifuge is operating and then permit preliminary data processing followed by transmission of the data to the DEC-10 computer for detailed analysis. This will result in significantly improved precision and enhanced facility in data acquisition and analysis, thus effecting a marked increase in efficiency of research as well as permitting studies where the precision of current methods has not been adequate, such as discriminating between two different models of macromolecular association which have very similar but not identical concentration distributions in the analytical ultracentrifuge. MLAB, operating on the DEC-10 computer, has been used for mathematical modeling studies for the analysis of various types of protein interactions. These studies have been applied to ultracentrifugal studies of binding and of protein self-association. Such studies are described in the annual report entitled Physical Chemistry of Biological Macromolecules.